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Thread: Lazy capstan solenoid

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    Lazy capstan solenoid

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    I have rotated my Teac A-6300 back into use and find that the capstan solenoid has become a bit lazy. What I mean is when i engage play, the brake solenoids release sharply but the capstan solenoid( in the same circuit loop) does sort of a "stutter click" when engaging and rather than sharply indexing the pinch roller over is a bit slow.
    In the auto revere mode, it sometimes does not activate at all....no activity from the solenoid. But it is not consistent. I have cleaned and gently lubed the solenoid plunger, and its travel is free. I can manually move the linkage with no binding.

    I do not believe the solenoid itself is at fault. There is a diode across the coil and a capacitor in there on some other terminals. Why so many wires to this unit?

    Anybody (Cory?) have any idea/suggestions on what to look for? Polling all you smart people before i jack up a beautiful machine by poking around......

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    I would start with the relay that powers the solenoid. I’m not familiar with that machine, but any corroded internal contacts/connections in plugs and switches could cause the symptoms you are experiencing. And then the relay. Same thing. Those are hard contact switches basically and if the contacts are oxidized/carbonized or otherwise corroded you can get intermittent results, or with the higher impedance in the circuit from bad contacts the relay action will be sluggish with the lower power, or the solenoid might not latch up because there’s not enough holding voltage. Usually there is initial power that comes from the switch through the relays, and when the relay contacts close there are other contacts the close to provide the holding power to the solenoid so that the solenoid stays powered even when you release the switch.

    Do you have the service manual?

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    I have the manual and schematics. I can see the relay that triggers the capstan solenoid, Just need to id it in the machine. Teac does a nice job of burying them.
    Would it help to measure the voltage at the coil??

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    Yeah it depends on the machine how hard stuff is to get to.

    If I get a chance I’ll see if I have that manual set somewhere so I can look at it alongside you.

    Yeah it’s a good idea to measure the voltage across the coil to support your determination it’s not a mechanical issue. I’m assuming it’s powered by a 24VDC supply but you’ll want to check that in the manual, and then measure when it’s under load. It should be at or close to the power rail’s intended voltage under load. If it’s not it can be a power supply fault but you say your other transport functions are okay so it’s *probably* safe to assume it’s not the supply, but it would *also* be a good idea to verify that when the pinch roller solenoid is powered. If the power rail looks good but the voltage is lower across the pinch roller solenoid coil then it’s something in between. You could also compare the voltage across other solenoids (brake and...is there a lifter solenoid?) to really get to the determination “yup, it’s something in between the power supply and the coil specific to the pinch roller solenoid.”

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    I cannot see anything i the manual indicating the voltage for the solenoid. My measurement across the coil was something in the range of 8 volts which seems low.
    The Brake solenoids are even lower than that but all 3 solenoids fire and when they are pulled in are pulled in firm.
    I guess my reference is my other TEAC machines (2340 and 3340) where the capstan pulls in hard when the play button is activated and the 6300 has a slight lag.
    But when its in its in firm...I mean I cannot pull the pinch roller back manually so it must have good hold voltage.
    The capstan delay is not killer but just a bit like a tic or a random squeak in a car...annoying but not impeding function.

    I am lately wondering if i need to exercise my machines on a more frequent basis......

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    I'm not sure if you're describing the common problem with these machines -I have something with my A-3340 as well.

    Here, it's the pivot post that the pinch roller assembly moves on, the grease in the thing has hardened over the years. Some machines have locked up seriously, some have varying degrees of problems with movement. The fix is to take the assembly apart, there is a YouTube video to illustrate for at least one of the 3??? machines. Take apart, and refresh the grease.

    Mine still works, but needs a little manual help to engage correctly. Once the machine is warmed up, then it operates a little better, so your reference to 'exercise' may be relevant.

    Does this sound like it might be relevant?

    Geoff

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    Thanks Geoff. I've had that assembly off in the past. When I got the machine many years back the prior owner had crudely modified the linkages in there, perhaps to have some sort of tape lifter defeat.
    I sourced the correct parts from a donor machine and restored all the mechanicals correctly, and got it all moving freely. It all still moves free, even in 'cold' state. Just has that lag in engaging the solenoid, and *sometimes*, randomly, it either does not pull in or doesn't pull in entirely. The relay is actuating, and the brake solenoids which appear to be in the same circuit drop out sharply. Which makes me feel the relay is ok......

    >>> I am tearing it apart to get at that relay just to be sure. Unfortunately Teac found it expedient (cheap) to solder the cube relay directly to the board rather than use a socket.

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    And i DID have that sticky problem on my 3340S as well, but it was rectified by cleaning and re-lube as you indicate.

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    Techno, just to be sure, is there a rubber washer to provide cushion when the solenoid plunger retracts? I suspect you considered that and ruled that out already, but those washers can turn to sticky goo just like other rubber parts and glue the solenoid in the retracted position causing it to extend slowly against grip of the tacky tendrils. Any chance that’s at play here?

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    All good there. I replaced the gooey one when i rebuilt the mechanism some years back. I have pretty much discounted any mechanical hangups.

    >> Interesting note: I did a test with the pinch rollers on my 2340S, 3340S, and the 6300. If I hold the pinch roller to keep it from pulling in when i activate the play mode, when I let go none of them will pull in.
    BUT, on the 2340 and 3340, if i then push the pinch roller up to the capstan (engaged position), the solenoid "grabs" and locks the roller in tight, suggesting a good "hold" current.
    On the 6300, that does not happen. The solenoid does not appear to have the current to even try to hold the puck in place.

    This befuddles me.

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